Continuous threads (fibre cable) spun from solvents and combined to form bands of many individual filaments pass through a number of after-treatment stages before being conveyed into the secondary spinning mill, that is into the yarn production apparatus.
The essential stages are washing to remove residual solvent, drawing, drying, crimping, crimp fixing and cooling.
Whereas the threads are conveyed through the washing and drying units with minimal covering density, i.e. as a thin band which is as wide as possible, during the washing and drying treatment in order to achieve optimum results, i.e. high degree of washing and drying, it is advantageous to carry out crimping, crimp fixing and cooling with as little apparatus as possible and this leads to a saving in processing and investment costs and also to a product of uniform quality.
In the past, for example, a sliver of a certain width was divided into several narrow silvers after washing and drying and each sliver was crimped in an individual crimping chamber, with the crimping chambers being arranged not next to one another but displaced behind each other for reasons of space, and, owing to the varied dwelling times of the bands between dryer and crimping unit, allowing for irregularly crimped band portions. It is now desirable to use only one crimping apparatus for a certain cable thickness in the form of a wide band in order to improve the quality of the product, in particular a uniform quality with respect to crimping, transverse adhesion of the cable, attainable carding rate, feel and dye holding capacity, to mention only a few important parameters.